Add Profanity Filter

[alexk2037]

Hello, this is a profanity filter for Vosk in response to issue https://github.com/alphacep/vosk-server/issues/110

It relies on two libraries, profanity-filter and alt-profanity-check, because I found that the combination performs faster than the profanity-filter alone, but still achieves the same accuracy (see this comment for more details).

[nshmyrev]

Thank you, let me try to play with this.